Metallurgical process



c. H. HUMPHRIES 2,260,670

METALLURGICAL PROCESS Oct. 28, 1941.

Filed Jan. 19, 1940 Ore +Au Micelle +X R0 H Tem.400C.

05 e Time-lOfol5min.

Comminuror To 100 Mesh Dilure HCI /4 gel. to lgol. per IOO lb. ore

Agitote until oc'rion ceoses 95%No2 CO3+ 5% D.S.P until pH is ll.51o|3 1-decon'r orange yellow Aerore 4 16 hrs. then settle unTil llquor slimefree 0.5.0., 0.5.0. E8. or S .O.A.

s m .01 to 1% No ON in Solution Aero're 4-!6 hrs.

TONS J Cherry red to Recover Au by P p "q known methods Recover Au byknown methods e/zz vezzi or' counties, State of 'Michigan.

Patented Oct. 28, 1941 UNITED STATES PATENT OFFICE METALLURGICAL PROCESSChad H. Humphries, Winnetka, 111-. Application January 19, 1940, SerialNo, 314,669 a 22 Claims.

This invention is concerned with methods of extracting gold fromsedimentary or argillaceous rocks or like substances, in which themetalis frequently found in finely divided form.

It has been known that gold is to be found in certain sedimentaryrocks,-a typical example being-limestone strata in Alpena andPresqueIsle Examination of these ores under high power microscopes does notordinarily disclose any visible gold particles, and it is inferred thatthe gold particles are ultra-microscopic and of a size ranging from afew millimicrons to perhaps one micron. These particles are hereinafterreferred to as micelle. Priorefforts to extract these micelle from thestrata in which they are found through conventional methods have provedfutile, although assay smelts at times show substantial values of theprecious metal, while identical smelts from comparable samplesfrequently reveal nothing more than a trace.

Methods for treating gold-bearing rock of this type are disclosed in thefollowing patent and copending application: Henry Jefis and Edward J.Dunn, Patent No.- 2\,193,234 issued March 12,

1940; James J. Bonesteel, Serial No. 276,671, filed May 31, 1939. Eachof these methods is concerned with transferring gold micelle from theore'to a'suspensoid of colloid state in Water, and the tails arerejected when-this has been accomplished. I have found that the tailsstillmay contain the major proportion of the values, after the ore hasbeen treated by these methods, and that with proper treatmentsubstantial values can be recovered from the tails through conventionalmethods.

The principal object of this invention then is to present methods fortreating gold-bearing material of the type described in such manner thatit is amenable to ordinary methods of capture, such as cyanidization,for. example.

It has been found that the limestone strata bearing the gold micellehave a tendency to be acidic, and likewis,e contain deleteriousmaterials composed principally! of hydrocarbons of the paraffin orolefine series, although for the purpose of applying the hereindescribed processes it is not necessary to define precisely the natureof these inhibiting ingredients. These organic compounds may composefrom .3% to .5% of the original aggregate by weight. It has been found,however, that, when such deleterious organic compounds are removed bythe methods hereinafter described, the gangue may then be treatedthrough conventional cyanide processes with satisfactory recoveries.

These methodsare diagrammatically shown in the attached flow sheet, inwhich the symbols utilized have the following significance: X refers tovarious unknowns, organic and inorganic, D. E. 0. refers to di-ethyloleate E, S. refers to ethyl stearate D. E. G. refers todi-ethyleneglycol S O. A. refers to sucrose-octa-acetate D. S. P. refersto di-sodium hydrogen phosphate The limestone rock containing themicellic gold particles is first broken into lumps roughly one-half inchin diameter and then subjected to roasting Any of the approved roastersmay be used, the principal roasting requirement being an application ofa temperature of approximtaely 400 C. for a 10t0 15 minute timeinterval. The application of the degree of heat for the period specifiedresults in driving off a majority of the organic material, leaving theremainder of the ore relatively in itsprevious chemical condition,although the-lumps of ore may be reduced in the roasting to the form ofa powder. Not all of the organic material is released, some free carbonremaining, but most, if not all, of the hydrogen present is driven off.It is to be noted that the heat specified is insufficient to reduce thelime, andthat little, if any, carbon dioxide should be given off duringthe roasting. j I

Where the limestone rock is still lumpy in form after the roasting iscompleted, it is desirable to comminute the same to pass 100 mesh orless, which assists the action of the hereafter described reagents.

When the roasting has been completed, the ore is then treated with avery dilute solution of hydrochloric acid, sufficient to react with ap.proximately 1% of its limestone content, Onequarter gallon to one gallonof solution should be used per 100 lbs. of ore. While the hydrochloricacid is working on the limestone, the mixture is agitated, preferably byair, until all action ceases, when the gangue is receptive for the nextstep in the process. If, however, "the roasting step. has beenefficacious in breaking up the organic compounds'the here describedtreatment with hydrochloric acid may be dispensed with.

While I prefer the preliminary roasting step which has been described,an equivalent is comminuation followed by treatment withhydrochloricacid in water, so, that the hydrochloric acid solutionamounts to approximtaely 2% of the entire volume. The mixture should bethoroughly aerated until all action ceases. Nitre cake may besubstituted for the hydrochloric acid, the nitre cake added amounting toapproximately 244% to 2 of the entire volume. Aeration is the same aswith hydrochloric acid. In addition, sulphuric acid may be mentioned asan equivalent for hydrochloric acid.

Whichever of the foregoing preliminary treatments is used, when the stephas been completed, a quantity of sodium carbonate is added as adispersing agent, which tends to disperse the gold micelle into ahydrosol. The quantity of sodium carbonate added must be sufiicient torender the mixture pronouncedly alkaline, with a pH from 11.5 to 13, andto assist the reaction the mixture should be subjected to furtheragitation, preferably by air, for a period of several hours, after whichit is allowed to settle until the top liquor is relatively free fromslimes. The reaction of the sodium carbonate plus agitation produces afroth in which all of the residual carbon is carried in a free form. Thetop liquor has an orange yellow color. In practice, sufiicient sodiumcarbonate to equal 2% of the entire solution has been found adequate.

In limestone rock which has been treated under this process, iron or itscompounds have frequently been found present, and they tend to inhibitthe dispersive effect of the sodium carbonate. In addition, it may beimpossible to add sufficient sodium carbonate to attain the desired pHof 11.5 to 13. In such cases I have found that the addition of a smallquantity of di-sodium hydrogen phosphate, amounting to about 5% of thesodium carbonate employed, will increase the pH or assist in the removalof the contaminating lI'OIl.

Di-sodium hydrogen phosphate may be substituted for sodium carbonate asa dispersing agent, although the cheapness of the sodium carbonaterecommends its use where cost is a consideration. Ammonium carbonate andammonium chloride are other equivalents which may be substituted forsodium carbonate.

The top liquor is then decanted or siphoned from the gangue, where it isready for additional treatment with a dispersing agent. I prefer todisperse the mixture by adding sufficient diethyl oleate, ethylstearate, di-ethylene glycol or sucrose-octa-acetate to equal, .01% to.1% of the entire solution. After agitation for a time interval of from4 to 16 hours, the dispersion is complete, the liquor beingcharacterized by a true colloidal-gold color from cherry red to purple,when, after coagulation of the colloid, the gold is extractable by knownmethods.

I have found that if much iron is present, the initial color in thesecond dispersion is rusty brown as a result of partial dispersion ofthe iron. In counteracting the effect of dispersion of the iron andexpediting dispersion of the gold micelle, I have found that the use ofsucrose-octa-acetate is especially effective, as it tends to coagulatethe iron dispersion, while dispersing the gold.

It is further to be understood that the limestone rock varies in itschemical complexity, and that some one of the organic dispersing agentsdescribed will be more effective with one ore than with another. When anew ore presents itself for processing, some experiment with thedescribed dispersing agents is necessary to determine which is the mostsuitable for the particular ore'which is the subject matter of inquiry.Where sulphur is present in the ore, and sodium poly-sulphides developas a product of the first dispersion, sucrose-octa-acetate isparticularly efficaceous in inhibiting their effects.

Some slimes may be carried in the decantation from the first dispersionto the second, and when they settle out or are captured throughfiltration, which should precede the coagulation step in recovering themassive gold from the colloid, they may be discarded or added to theoriginal tailings for the hereafter described cyanide leaching processto which the latter are subjected following the first dispersion.

While I believe the foregoing description of the dispersion stepsproduces the best results, as an alternative, separate dispersions canbe dispensed with, and the inorganic and organic dispersing agents canbe added simultaneously following the described treatment withhydrochloric acid or nitre cake.

Under this method of procedure, approximately 2% of sodium carbonate andapproximately .1% to 1% of one of the described organic dispersingagents may be added, the percentage expressed being of the entiresolution. The mixture is agitated, preferably by air, for a substantialperiod, and then allowed to settle until relatively clear, 18 hoursshould sufiice, during which the hydrosol', with a characteristic goldcolloid color, will form.

After the hereinbefore described pre-treatment of the tails anddecantation of the top liquor, following the first dispersion, the tailsare now amenable to treatment through recognized cyanide processes. Inpractice I prefer to use sodium cyanide plus aeration and agitation, allof which steps are well-known in the metallurgical arts.

As an equivalent of cyanidization, the gold may likewise be capturedthrough chlorination, a process which is likewise well-known.

By following the herein described process, it will be found that verysubstantial values can be recovered from gold-bearing limestone hithertosupposed to have been wholly unamenable to treatment by any commercialprocess. In numerous tests on limestones from Alpena and Presque IsleCounties in Michigan, I have found an astonishing correlation of thevalues recovered through dispersion of the top liquor, and the valuesrecovered from the tails by cyanidization after the describedpre-treatment of the gangue. Numerous tests on comparable two-pound oresamples have indicated that from 4 to 6 mgm. of gold may be recoveredthrough dispersion of the top liquor, and from 15 to 20 mgm. of gold cansubsequently be recovered from the tails by cyanidization, whereas, ifthe ore were not treated as here described, but immediately subjected toordinary cyanidization processes, it would be completely irresponsivethereto.

The following tabulation covers the results of fire assays and test runsunder the herein described process, on three two-pound samples of ore.

Having fully described my invention, I claim: 1. In the art ofrecovering gold micelle from sedimentary or argillaceous rock containinginhibiting organic compounds, that process which includes first removingsaid compounds without materially decomposing the ore, then treating theore with a dispersing agent and partially dispersing the gold micelleinto a hydrosol, then decanting the top liquor, and recovering'theundispersed micelle from the residue by known methods.

2. In the art of recoveringgold micelle from sedimentary or argillaceousrock containing inhibiting organic compounds, that process whichincludes first removing said compounds without materially decomposingthe ore, then treating the ore with a dispersing agent and partiallydispersing the gold micelle into a hydrosol, then decanting the topliquor, recovering the undispersed micelle from the residue by knownmethods, redispersing the top liquor with a dispersing agent andagitating the same until the gold micelle remaining therein are in adisperse or colloid'state, and then recovering the dispersed gold fromthe colloid.

3. In theart of recovering gold micelle" from sedimentary orargillaceous rock containing inhibiting organic compounds,'that processwhich includes first removing said compounds without materiallydecomposing the ore, then treating the ore with a dispersing agent andpartially dispersing the gold micelle into a hydrosol, then decantingthe top liquor, redispersing the top liquor with a dispersing agentand'agitatingthe same until the gold micelle remaining therein are in adisperse or colloid state-and then recovering the dispersed gold fromthe colloid. I

- 4. In the art of recovering gold micelle 'from sedimentary orargillaceous rock containinginhibiting organic compounds and having apHof slightly. less than '7,- that process which includes first removingsaid compounds without materially decomposing the ore, then. treatingthe ore with. a-dispersing agent ofa nature and in sufiicient amount togive the pulp a distinctly basic pH, at the same timepartially-dispersing the gold micelle into a gold hydrosol, then -decanting the top liquor and recovering the undis persed .micelle 'fromthe I, residue .-byknown methods. A a

5. In the art of recovering gold micelle from sedimentary or.argillaceous 'rock containing in hibiting organic compounds and havingapH of slightly less than 7, that process whichincludes first removingsaid compounds without materially decomposing the ore, then-treating theore with a dispersing agent of a natureand in sufficient amount, to givethe pulp a-distinctly basicrpH, atthe sametime partially dispersing thegold micelle into a gold hydrosol, then adding a second dispersing agentandv agitating the liquor until the formation of r a gold hydrosol iscompleted, and then recovering the dispersed gold from the hydrosoL. l6. In the art of preparingoreghaving, a pH of slightly less than 7 andcontaining gold micelle and inhibiting. organic compounds fortreatmentthose. stepslwhich include, first. removing said vcompoundswithout materially idecomposing the .ore, followed by treatment of .theore with adispersing agent of a. nature and in sufficient amount togive.the ore a distinctly basic pH. l '7. In the art of recovering goldmicelle from sedimentary or argillaceous rock, that process whichincludes roasting the ore at a temperature sufficient to break down orfree any organic compounds present in the ore, leaving no more than somefree carbon remaining after said roasting, saidroasting temperaturebeing insufficient to decompose the ore, oomminuting the ore subsequentto the roasting if in the roasting step the ore has not beensufficiently powdered, subjecting the powdered or comminuted ore to adilute hydrochloric acid solution sufficient to react with approximatelyone per cent. of the ores content, if said roasting has not entirelybroken down or freed said organic compounds, subsequently treating thecomminuted or powdered ore with a dispersing agent and partiallydispersing the micelle from the ore into the liquor, decanting the topliquor upon completion of the dispersion step, and recovering theundispersed micelle from the residue through known methods.

8. In the art of recovering gold micelle from sedimentary orargillaceous rock, that process which includes roasting the oreat atemperature sufiicient to break down or free any organic compoundspresent in the ore, leaving no more than some free carbon remainingafter said roasting, said roasting temperature being insufficient todecompose the ore, oomminuting the ore subsequent to the roasting if inthe roasting step the ore has not been sufliciently powdered, subjectingthe powdered or comminuted or'e to a dilute hydrochloric acid solutionsuificient to react with approximately one per cent. of the orescontent, if said roasting has not entirely.

broken down or freed saidorganic compounds, subsequently treating thecomminuted or powdered ore with a dispersing agent, decanting the topliquor upon completion of the dispersion step; redispersing the topliquor with a dispersing agentand agitating the same" until the goldmicelle are in a disperse or colloid state in the top liquor, andsubsequently recovering the gold from thecolloid,

9. In the art of recovering gold micelle from sedimentary orargillaceous rock containing'organic compounds, that process whichincludes oomminuting the ore, treating the same 'with'a hydrochloricacid solution, said solution amounting to approximately two percent.of'the' entirevolume, or withnitre cake in substantially similar amount,thoroughly agitating the solution-after the hydrochloric acid or nitrecake has been added until all "action ceases, subsequently adding adispersing agent and partially dispersing the micelle into thetopliquor, decanting the top liquor after the dispersion, and recoveringthe micelle from the residue by known methods.

10. In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich includes comminuting'the ore, treating the same with ahydrochloricacid solution, said solution amounting toapproximately twoper cent. of the entire volume, or with nitre cake in substantiallysimilar amount, thoroughly agitating the-solue tion until all actionceases, subsequently-adding a dispersing agent to-the top liquor andfurther agitating the-solution, settling the solution subsequent to theagitation, decanting the top liquor, redispersing the top liquor with adispersing agent, agitating-and then settling the same until a goldhydrosol is formed, and recovering the dispersed gold from the hydrosol11. In the art of recoveringgold micelle from, sedimentary orargillaceous rock, thatprocess which includes roasting the ore at atemperature sufiicient to break down or free any organic cornpoundspresent in the ore, leaving no more than some free carbon remainingafter said roasting,

said roasting temperature being insufiicient to decompose the ore,comminuting the ore subsequent to the roasting if in the roasting stepthe ore has not been sufficiently powdered, subjecting the powdered orcomminuted ore to a dilute hydrochloric acid solution sufiicient toreact with approximately one per cent .of the ores content if saidroasting has not entirely broken down or freed said organic compounds,simultaneously treating the comminuted or powdered ore with an inorganicand an organic dispersing agent, and partially dispersing the micellefrom the ore into the top liquor, decanting the top liquor uponcompletion of the dispersion step, and recovering the undispersedmicelle from the residue through known methods.

12. In the art of recovering gold micelle from sedimentary orargillaceous rock, that process which includes roasting the ore at atemperature sufficient to break down or free any organic compoundspresent in the ore, leaving no more than some free carbon remainingafter said roasting, said roasting temperature being insufiicient todecompose the ore, comminuting the ore subsequent to the roasting if inthe roasting step the ore has not been sufiiciently powdered, subjectingthe powdered or comminuted ore to a dilute hydrochloric acid solutionsufiicient to react with approximately one per cent. of the orescontent, if said roasting has not entirely broken down or freed saidorganic compounds, subsequently treating the comminuted or powdered orewith an inorganic dispersing agent of a nature and in sufficient amountto give the top liquor and residue a pronounced alkalinity and partiallydispersing the micelle from the ore into the top liquor, decanting thetop liquor upon completion of the dispersion step, and recovering theundispersed micelle from the residue through known methods 13. In theart of recovering gold micelle from sedimentary or argillaceous rock,that process which includes roasting the ore at a temperature sufiicientto break down or free any organic compounds present in the ore, leavingno more than some free carbon remaining after said roasting, saidroasting temperature being insufiicient to decompose the ore,comminuting the ore subsequent to the roasting if in the roasting stepthe ore has not been sufficiently powdered, subjecting the powdered orcomminuted ore to a dilute hydrochloric acid solution sufiicient toreact with approximately one per cent. of the ores content if saidroasting has not entirely broken down or freed said organic compounds,subsequently treating the comminuted or powdered ore with an inorganicdispersing agent of a nature and in sufficient amount to give the topliquor and residue a pronounced alkalinity, decanting the top liquorupon completion of the dispersion step, redispersing the top liquor withan organic dispersing agent, combined with agitating the same until agold hydrosol is formed and sub sequently recovering the dispersed goldtherefrom.

14. In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich includes comminuting the ore, treating the same with ahydrochloric acid solution, said solution amounting to approximately twoper cent. of the entire volume, or with nitre cake in substantiallysimilar amount, thoroughly agitating the solution until all actionceases, subsequently adding an inorganic dispersing agent to the top,liquor of a nature and in sufiicient amount to give the top liquor andresidue a pronounced alkalinity, and partially dispersing the micellefrom the ore into the top liquor, further agitating the solution untilthe dispersion is completed, and settling the solution subsequent to theagitation, decanting the top liquor after the dispersion, and recoveringthe undispersed micelle from the residue by known methods.

l5.-In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich includes comminuting the ore, treating the same with ahydrochloric acid solution, said solution amounting to approximately twoper cent. of the entire volume, or with nitre cake in substantiallysimilar amount, thoroughly agitating the solution until all actionceases, subsequently adding an inorganic dispersing agent of a natureand in sufficient amount to give the top liquor and residue a pronouncedalkalinity, further agitating the solution and settling the samesubsequent to the agitation, decanting the top liquor, redispersing thetop liquor with an organic dispersing agent, agitating and then settlingthe same until a gold hydrosol is formed, and recovering the dispersedgold from the hydrosol.

16. In the art of recovering gold micelle from sedimentary orargillaceous rock, that process which includes roasting the ore at atemperature of approximately 400 C. for a period of from 10 to 15minutes, without decomposing the ore, comminuting the ore subsequent tothe roasting if in the roasting step the ore has not been suflicientlypowdered, subjecting the powdered or comminuted ore to a dilutehydrochloric acid solution suflicient to react with approximately oneper cent. of the ores content, subsequently treating the comminuted orpowdered ore with a dispersing agent, decanting the top liquor uponcompletion of the dispersion step, recovering the micelle remaining inthe residue after dispersion and decantation through known methods,redispersing the top liquor with a dispersing agent, agitating and thensettling the same until a gold hydrosol is formed and recovering thedispersed gold from the hydrosol.

1'7. In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich includes roasting the ore at a temperature sufficient to breakdown or free said organic compounds, leaving no more than some freecarbon remaining after said roasting, said roasting temperature beinginsufficient to decompose the ore, comminuting the ore subsequent to theroasting if the roasting step in the'process has not suflicientlypowdered the same, subjecting the powdered or comminuted ore to a dilutehydrochloric acid solution sufficient to react with approximately oneper cent. of its content, if said roasting has not entirely broken downor freed said organic compounds, subsequently treating the comminuted orpowdered ore with an inorganic dispersing agent of suificient alkalinityto give the top liquor and residue a pH of from 11.5 to 13, andpartially dispersing the micelle into the top liquor, decanting the topliquor upon completion of the dispersion step, and recovering theundispersed micelle from the residue through known methods.

18. In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich ing the ore subsequent to the roasting if the roasting step in theprocess has not sufficiently the same until a gold hydrosol is formed,and

subsequently recovering the gold therefrom.

19. In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich includes comminuting the ore, treating the same with ahydrochloric acid solution, said solution amounting to approximately twoper cent. of the entire volume, or with nitre cake in substantiallysimilar amount, combined with thorough agitation until all actionceases, dispersing with an inorganic dispersing agent of sufficientalkalinity to give the top liquor and residue a pH of from 11.5 to 13,combined with further agitation until the micelle are partiallydispersed into the top liquor, settling subsequent to the agitation, de-7 canting the top liquor after the dispersion and recovering theundispersed micellefrom the residue by known methods.

20. In the art of recovering gold micelle from sedimentary orargillaceous rock containing inhibiting organic compounds, that processwhich includes comminuting the ore, treating the same with ahydrochloric acid solution, said solution amounting to approximately twoper cent. of the entire volume, or with nitre cake in substantiallysimilar amount, combined with thorough agitation until all actionceases, dispersing with an inorganic dispersing agent of sufficientalkalinity to give the top liquor and residue a pH of from 11.5 to 13,combined with further agitation and settling subsequent to theagitation, decantation of the top liquor, redispersing with an organicdispersing agent, and then settling the same until a gold hydrosol isformed, and recovering the dispersed gold from the hydrosol.

21. In the art of recovering gold micelle from ores having a pH ofslightly less than 7, those steps comprising subjecting the ore to aninorganic dispersing agent in sufficient amounts to give the ore and topliquor a pronouncedly alkaline pH, decanting the top liquor andredispersing the same with an organic dispersing agent.

22. In the art of recovering gold micelle from sedimentary orargillaceous rock having a pH of slightly less than 7, the use of adispersing agent composed of sodium carbonate and di-sodium hydrogenphosphate in the proportions of approximately 95 of the former to 5 ofthe latter.

CHAD H. HUNLPHRIES.

